Cancer (neoplasia) is characterized by deregulated cell growth and cell division. There are numerous types of cancers. Examples of cancers include prostate cancer and breast cancer.
Prostate cancer, as its name indicates, is a cancer that develops in the prostate gland of the male reproductive system. Prostate cancer can be aggressive, in which cancer cells metastasize and move from the prostate gland to other parts of the body, such as the lymph nodes and the bones. It is the second leading cause of cancer-related death in men in the U.S., and its prevalence is increasing in developing countries.
Prostate cancer growth is often driven by male sex hormones called androgens, which include testosterone. Because of this, a common treatment option for the 22% or 35,200 patients that cannot be treated with surgery, radiation, cryotherapy or watchful waiting is to lower the levels of androgens in the man's body. Androgen levels can be lowered by surgically removing the testicles or with drugs that stop the testicles, and to a lesser extent adrenal glands, from making androgens or block how they affect the body. This type of treatment is called hormonal therapy or androgen-deprivation therapy. Unfortunately, 40,000 patients each year begin to fail hormonal therapy or become hormone refractory. That is, they develop castration-resistant prostate cancer (CRPC) or hormone refractory prostate cancer (HRPC). Nevertheless, CRPC tumors typically continue to produce the androgen receptor (AR). CRPC tumors may continue to depend on AR for growth by producing greatly elevated levels of AR or by producing variant forms of AR in addition to the normal AR. Treatment options for prostate cancer are very limited once the disease becomes resistant to hormonal therapy through these or any other mechanisms.
Breast cancer is the fifth most common cause of cancer death in the world. In the U.S., breast cancer is the most common cancer diagnosed in women, and the second most common cause of cancer death in women. The treatment of breast cancer depends on various factors including stage of the cancer and age of the patient. Breast cancer is usually treated with surgery, such as lumpectomy or mastectomy followed by medication and/or radiation therapy. Medication includes hormone-blocking agents, chemotherapeutic agents, and monoclonal antibodies.
Although the focus of breast cancer research has been on estrogen receptor a (ER) signaling, androgens are known to play a role in normal breast physiology and therefore androgen receptor (AR) signaling is recognized as an important contributor towards breast carcinogenesis. Moreover, it appears that AR is expressed in many breast cancers, which makes AR an attractive therapeutic target.